1. Field of the Invention
The subject invention relates to a light emitting assembly of the type including light emitting diodes (L.E.D.s), and more particularly, reducing temperatures to prolong the service life of the L.E.D. light emitting assembly.
2. Description of the Prior Art
Light assemblies including L.E.D.s are often preferred over other light assembles due to their high efficiency. At least a fifty percent (50%) energy savings is possible when light assemblies including most high intensity discharge (H.I.D.) lights are replaced with properly designed L.E.D. light assemblies. An example of such an L.E.D. light assembly is disclosed in P.C.T. Patent Application Serial No. PCT/US2008/65874 to the present inventor, Peter A. Hochstein, which is directed to effective thermal management of an L.E.D. light emitting assembly. The '874 application discloses a heat sink presenting a mounting surface and an oppositely facing heat transfer surface and a plurality of light emitting diodes disposed on the mounting surface. The '874 application also discloses a housing disposed over the heat sink and presenting a top surface facing outwardly. Such L.E.D. light assemblies typically have a service life of about 70,000 hours.
Like most electrical assemblies, L.E.D. light emitting assemblies typically include electronics enclosures for covering a power supply and other electrical components. The electronic enclosure may be disposed on the top surface of the housing. However, the electrical components of L.E.D. light emitting assemblies are particularly subject to thermal damage, and are rarely designed to exceed 85° C. For example, when the electronics enclosure of an L.E.D. light emitting assembly is exposed to sunlight with a nominal radiant flux of 1000 W/m2 with an ambient air temperature of 20° C., the measured temperature inside the electronics enclosure typically exceeds 85° C., which causes the electrical components housed therein to fail before the light emitting diodes. Further, most geographical regions of the continental United States are subject to a solar flux of nominally 1,000 W/m2, which causes an electronics enclosure of even modest dimensions to absorb over 200 W of heat under direct sunlight.
One approach used to reduce the temperature inside the electronics enclosure includes venting the electronics enclosure. However, this approach is not practical because the electronics enclosure should be sealed against moisture, dirt, insects, and corrosive elements, such as salt or vehicle emissions, to maintain reliable operation.
Another approach used to reduce the temperature inside an electronics enclosure includes extending a solar shield over the electronics enclosure. An example of such a solar shield is disclosed in U.S. Pat. No. 5,986,618, in the name of Aakula et. al., and assigned to Lucent Technologies, Inc. The '618 patent discloses a solar shield having a continuous and closed solar top wall extending between solar ends and solar sides. The solar top wall of the '618 patent extends over and is spaced from the electronics enclosure to create a space therebetween. The solar shield of the '618 patent includes solar side walls depending from each of the solar sides to lower edges. Although the solar shield disclosed in the '618 patent blocks solar light from the electronics enclosure, the measured temperature inside the electronics enclosure is high.